Field of the Invention
The present invention relates to a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a non-aqueous electrolyte secondary battery that includes lithium iron phosphate in a positive electrode.
Moreover, this application claims priority on the basis of Japanese Patent Application No. 2014-001929, which was filed on 8 Jan. 2014, and the entire contents of that application are incorporated by reference in this specification.
Description of the Related Art
In recent years, non-aqueous electrolyte secondary batteries have been widely used as so-called portable power sources for personal computers, hand-held terminals and the like and as power supplies for vehicle propulsion. Of these, lithium ion secondary batteries, which can achieve high energy density while being light weight, can be advantageously used as high output motive power sources in vehicles such as electric vehicles and hybrid vehicles.
Layered materials such as lithium-cobalt composite oxides (LiCoO2) and lithium-nickel-cobalt-manganese composite oxides (for example LiNi0.33Co0.33Mn0.33O2), spinel type materials such as a lithium-manganese composite oxide (LiMn2O4) and olivine type materials such as lithium iron phosphate (LiFePO4) are known as positive active material materials able to be used in such batteries. For example, Japanese Patent Application Laid-open No. 2001-307730 indicates that by using a composite material obtained by mixing a layered material (LiCoO2) and an olivine type material (LiFePO4) at a prescribed weight ratio as a positive active material, it is possible to achieve stable charging and discharging characteristics.